Breakup of Air Bubbles in Water: Memory and Breakdown of Cylindrical Symmetry

Using high-speed video, we have studied air bubbles detaching from an underwater nozzle. As a bubble distorts, it forms a thin neck which develops a singular shape as it pinches off. As in other singularities, the minimum neck radius scales with the time until breakup. However, because the air-water interfacial tension does not drive breakup, even small initial cylindrical asymmetries are preserved throughout the collapse. This novel, non-universal singularity retains a memory of the nozzle shape, size and tilt angle. In the last stages, the air appears to tear instead of pinch.Comment: Submitted to Phys. Rev. Lett. 4 pages, 4 figures. Revised for resubmissio

Still water: dead zones and collimated ejecta from the impact of granular jets

When a dense granular jet hits a target, it forms a large dead zone and ejects a highly collimated conical sheet with a well-defined opening angle. Using experiments, simulations, and continuum modeling, we find that this opening angle is insensitive to the precise target shape and the dissipation mechanisms in the flow. We show that this surprising insensitivity arises because dense granular jet impact, though highly dissipative, is nonetheless controlled by the limit of perfect fluid flow.Comment: 5 pages, 5 figures, submitted to Physical Review Letter

Dense Suspension Splat: Monolayer Spreading and Hole Formation After Impact

We use experiments and minimal numerical models to investigate the rapidly expanding monolayer formed by the impact of a dense suspension drop against a smooth solid surface. The expansion creates a lace-like pattern of particle clusters separated by particle-free regions. Both the expansion and the development of the spatial inhomogeneity are dominated by particle inertia, therefore robust and insensitive to details of the surface wetting, capillarity and viscous drag.Comment: 4 pages (5 with references), and a total of 4 figure

Corporate governance and the informativeness of disclosures in Australia:a re-examination

We re-examine the association between corporate governance and disclosures reported by Beekes and Brown (2006), using an extended time series of Australian data. Since the ASX corporate governance guidelines were introduced in 2003, firms generally have increased their disclosure frequency and demonstrated an improvement in the timeliness of bad news relative to good news, indicating a levelling of disclosure practices and greater transparency. Better governed firms have become more cautious in their disclosure practices. However they continue to be more balanced with respect to good and bad news timeliness. Changes to disclosure laws have also influenced company practices

Financial integration and the transparency of firms in emerging capital markets

We examine the association between financial integration and capital market transparency of emerging-market firms. We use four intra-year price timeliness measures derived from the Beekes and Brown (2006, 2007) methods as indicators of the firm’s transparency. The sample comprises 57,465 firm-year observations on listed companies in 24 emerging economies over the period 1995-2010. As expected, we find that greater financial integration is associated with greater transparency, and that the effect is more pronounced when the news about the firm is bad. Using structural equation modelling (SEM), we find evidence of a mechanism through which financial integration enhances the information environment: improved corporate governance